The Mis-Splicing Events in Lr34 Transcripts in Wheat

Wheat (Triticum aestivum, 2n=6x=42, AABBDD) is a major food crop worldwide, and this crop is constantly challenged by leaf rust caused by Puccinia triticina. Lr34 is a non-race-specific gene that confers resistance against fungal pathogens including leaf rust, stripe rust, stem rust, and powdery mildew, as well as barley yellow dwarf virus, and it cosegregates with the morphological marker, leaf tip necrosis. Because of the durability and non-specificity of its resistance against multiple pathogens, Lr34 has become one of the most important disease-resistance genes in wheat worldwide and has been utilized since the mid-20th century. In this study, we found that in a cultivar carrying the resistant Lr34 allele, only a portion of its transcripts was correctly spliced. The majority of Lr34 transcripts was incorrectly spliced due to multiple intron retention or exon skipping events. The proportion of mis-spliced transcripts of Lr34 was mediated by low temperature and by plant age. When resistant Lr34 cDNA was over-expressed in a cultivar that carries the resistant allele, functional Lr34 transcripts increased in number and the adult transformed plant displayed near immunity to leaf rust. These findings suggest that the level of resistance from a partial resistance gene can be increased to a significantly higher level by eliminating or mutating regulators which cause mis-splicing events.